This is a timeline of category theory and related mathematics. Its scope ("related mathematics") is taken as:
Categories of abstract algebraic structures including representation theory and universal algebra;
Homological algebra;
Homotopical algebra;
Topology using categories, including algebraic topology, categorical topology, quantum topology, low-dimensional topology;
Categorical logic and set theory in the categorical context such as algebraic set theory;
Foundations of mathematics building on categories, for instance topos theory;
Abstract geometry, including algebraic geometry, categorical...